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About RFID/NFC RC522 Module and Solenoid Lock
If you do not know about RFID/NFC RC522 Module and solenoid lock (pinout, how it works, how to program ...), learn about them in the following tutorials:
This image is created using Fritzing. Click to enlarge image
To simplify the setup, the pins of the RC522 module are directly connected to the Arduino pins. However, this direct connection may lead to issues, as the output pins of the Arduino provide 5V, while the RC522 module's pins are designed for a 3.3V operation. It is advisable to regulate the voltage between the Arduino pins and the RC522 module's pins to prevent potential problems. For more detailed guidance, please consult the Arduino - RFID RC522 tutorial. The provided diagram illustrates how resistors can be employed to regulate the 5V to 3.3V:
This image is created using Fritzing. Click to enlarge image
※ NOTE THAT:
The order of pins can vary according to manufacturers. ALWAYS use the labels printed on the module. The above image shows the pinout of the modules from DIYables manufacturer.
Arduino Code - Single RFID Tag
/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-rfid-solenoid-lock */#include <SPI.h>#include <MFRC522.h>#define SS_PIN 10#define RST_PIN 5#define RELAY_PIN A5 // The Arduino pin that controls the solenoid lock via relayMFRC522 rfid(SS_PIN, RST_PIN);byte authorizedUID[4] = {0xFF, 0xFF, 0xFF, 0xFF};voidsetup() {Serial.begin(9600);SPI.begin(); // init SPI bus rfid.PCD_Init(); // init MFRC522pinMode(RELAY_PIN, OUTPUT); // initialize pin as an output.digitalWrite(RELAY_PIN, LOW); // deactivate the solenoid lock => lockedSerial.println("Tap RFID Tag on reader");}voidloop() {if (rfid.PICC_IsNewCardPresent()) { // new tag is availableif (rfid.PICC_ReadCardSerial()) { // NUID has been readedMFRC522::PICC_Type piccType = rfid.PICC_GetType(rfid.uid.sak);if (rfid.uid.uidByte[0] == authorizedUID[0] && rfid.uid.uidByte[1] == authorizedUID[1] && rfid.uid.uidByte[2] == authorizedUID[2] && rfid.uid.uidByte[3] == authorizedUID[3] ) {Serial.println("Authorized Tag");digitalWrite(RELAY_PIN, LOW); // deactivate the solenoid lock => unlockeddelay(2000);digitalWrite(RELAY_PIN, HIGH); // activate the solenoid lock => locked }else {Serial.print("Unauthorized Tag:");for (int i = 0; i < rfid.uid.size; i++) {Serial.print(rfid.uid.uidByte[i] < 0x10 ? " 0" : " ");Serial.print(rfid.uid.uidByte[i], HEX); }Serial.println(); } rfid.PICC_HaltA(); // halt PICC rfid.PCD_StopCrypto1(); // stop encryption on PCD } }}
Quick Steps
Because UID is usually not printed on RFID Tag, The first step we need to do is to find out the tag's UID. This can be done by:
Copy the above code and open with Arduino IDE
Click Upload button on Arduino IDE to upload code to Arduino
Open Serial Monitor
Tap an RFID Tag on RFID-RC522 module
Get UID on Serial Monitor
Newbiely | Arduino IDE 2.3.8
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File
Edit
Sketch
Tools
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Arduino Uno
Newbiely.ino
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8Serial.println("Hello World!");
Output
Serial Monitor
Message (Enter to send message to 'Arduino Uno' on 'COM15')
New Line
9600 baud
Tap RFID Tag on reader
Unauthorized Tag: 51 3D C1 AC
Ln 11, Col 1
Arduino Uno on COM15
2
After having UID:
Update UID in the line 18 of the above code. For example, change byte authorizedUID[4] = {0xFF, 0xFF, 0xFF, 0xFF}; TO byte authorizedUID[4] = {0x51, 0x3D, 0xC1, 0xAC};
Upload the code to Arduino again
Tap an RFID Tag on RFID-RC522 module
See output on Serial Monitor
Newbiely | Arduino IDE 2.3.8
──
☐
✕
File
Edit
Sketch
Tools
Help
Arduino Uno
Newbiely.ino
···
8Serial.println("Hello World!");
Output
Serial Monitor
Message (Enter to send message to 'Arduino Uno' on 'COM15')
New Line
9600 baud
Tap RFID Tag on reader
Authorized Tag
Ln 11, Col 1
Arduino Uno on COM15
2
Tap another RFID Tag on RFID-RC522 module
See output on Serial Monitor
Newbiely | Arduino IDE 2.3.8
──
☐
✕
File
Edit
Sketch
Tools
Help
Arduino Uno
Newbiely.ino
···
8Serial.println("Hello World!");
Output
Serial Monitor
Message (Enter to send message to 'Arduino Uno' on 'COM15')
New Line
9600 baud
Tap RFID Tag on reader
Authorized Tag
Unauthorized Tag: 5D 11 1A D3
Ln 11, Col 1
Arduino Uno on COM15
2
Arduino Code - Multiple RFID Tags
We can allow multiple RFID/NFC tags to activate the solenoid lock. The below code uses two tags as an example.
/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-rfid-solenoid-lock */#include <SPI.h>#include <MFRC522.h>#define SS_PIN 10#define RST_PIN 5#define RELAY_PIN A5 // The Arduino pin that controls the solenoid lock via relayMFRC522 rfid(SS_PIN, RST_PIN);byte authorizedUID1[4] = {0x51, 0x3D, 0xC1, 0xAC};byte authorizedUID2[4] = {0x30, 0x01, 0x8B, 0x15}; voidsetup() {Serial.begin(9600);SPI.begin(); // init SPI bus rfid.PCD_Init(); // init MFRC522pinMode(RELAY_PIN, OUTPUT); // initialize pin as an output.digitalWrite(RELAY_PIN, LOW); // deactivate the solenoid lock => lockedSerial.println("Tap RFID Tag on reader");}voidloop() {if (rfid.PICC_IsNewCardPresent()) { // new tag is availableif (rfid.PICC_ReadCardSerial()) { // NUID has been readedMFRC522::PICC_Type piccType = rfid.PICC_GetType(rfid.uid.sak);if (rfid.uid.uidByte[0] == authorizedUID1[0] && rfid.uid.uidByte[1] == authorizedUID1[1] && rfid.uid.uidByte[2] == authorizedUID1[2] && rfid.uid.uidByte[3] == authorizedUID1[3] ) {Serial.println("Authorized Tag 1");digitalWrite(RELAY_PIN, LOW); // deactivate the solenoid lock => unlockeddelay(2000);digitalWrite(RELAY_PIN, HIGH); // activate the solenoid lock => locked }elseif (rfid.uid.uidByte[0] == authorizedUID2[0] && rfid.uid.uidByte[1] == authorizedUID2[1] && rfid.uid.uidByte[2] == authorizedUID2[2] && rfid.uid.uidByte[3] == authorizedUID2[3] ) {Serial.println("Authorized Tag 2");digitalWrite(RELAY_PIN, LOW); // deactivate the solenoid lock => unlockeddelay(2000);digitalWrite(RELAY_PIN, HIGH); // activate the solenoid lock => locked }else {Serial.print("Unauthorized Tag:");for (int i = 0; i < rfid.uid.size; i++) {Serial.print(rfid.uid.uidByte[i] < 0x10 ? " 0" : " ");Serial.print(rfid.uid.uidByte[i], HEX); }Serial.println(); } rfid.PICC_HaltA(); // halt PICC rfid.PCD_StopCrypto1(); // stop encryption on PCD } }}
Do the similar steps as the above, and then tap one by one tag on RFID-RC522 module. The result on Serial Monitor looks like below:
Newbiely | Arduino IDE 2.3.8
──
☐
✕
File
Edit
Sketch
Tools
Help
Arduino Uno
Newbiely.ino
···
8Serial.println("Hello World!");
Output
Serial Monitor
Message (Enter to send message to 'Arduino Uno' on 'COM15')
New Line
9600 baud
Tap RFID Tag on reader
Authorized Tag 2
Authorized Tag 1
Ln 11, Col 1
Arduino Uno on COM15
2
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